Because the submerged pump is inserted into the bottom portion inside the casing which has been vertically lowered inside the tank, the power supplying unit against the motor for driving this pump is installed air-tightly, with use of a flange, to the bulkhead in the boundary area between the casing interior and the atmosphere. Therefore, the unit is subjected to the actions as follows.
a. The unit is subjected to the temperature influence close to the atmospheric temperature in the case that the pump is not put into operation.
b. When the power supply for running the pump is started the penetrating conductor for power supply initially heats up to around 80.degree. to 90.degree. C. When the scooping of low temperature liquid is commenced, the conductor is cooled down sharply by the influence of the low-temperature liquid or gas.
Since the penetrating conductor of power supplying unit is especially and repeatedly subjected to this type of heat influence, the conductor repeats the linear expansion and contraction at each of the occasions. There exists a possibility for breakages to the air-tightly connected area of penetrating conductor because of the stress being generated by this phenomenon. Therefore, in the conventional design, a ceramic sleeve 4 is passed through and fixed to the inside of mount hole 2 of flange 1 which is fitted to the bulkhead "d" of, and replace casing as shown in FIG. 5. Through the ceramic sleeve a penetrating conductor 5 is passed, wherein the ceramic sleeve 4 is air-tightly coupled to the penetrating conductor 5 by use of a silver solder 7 utilizing a metallic plate 6 on the inside of the flange 1 (casing interior). This is done with such a contrivance that no stress may act especially on the ceramic sleeve 4 and the silver solder 7 area having small tensile strengths by putting the outside of flange 1 from the inside of ceramic sleeve 4 under a free situation and by directing the linear expansion and contraction of penetrating conductor 5 toward the outside direction of flange 1.
However, in the event that the ceramic sleeve 4 has been air-tightly connected sealingly to the penetrating conductor 5 only at one location inside the flange in this way, the low temperature liquid or gas may promptly leak out of the inside of casing, resulting in a dangerous situation if any breakage should happen to this sealed area and the airtightness should be damaged.